Electric circuit breaker having arcerosion distributing means



Dec. 17, 1963 M. L. HEINTZ ELECTRIC CIRCUIT BREAKER HAVING ARC-EROSION DISTRIBUTING MEANS Filed Oct. 3, 1960 Inventor: Milton 1.... Heintz,

Attorney.

United States Patent 1 3,114,817 ELECTRIC QERQUIT BREAKER HAVING ARC- ERGSHGN DISTRIBUTING MEANS Milton L. Heintz, Newtown Square, Pa, assignor to General Electric Qompany, a corporation of New York Filed (let. 3, 1969, Ser. No. 6%,4526 9 (Claims. (til. Nil-16d) This invention relates to an electric circuit breaker and, more particularly, to means for prolonging the useful life of the contacts of the circuit breaker.

The useful life of a set of circuit breaker contacts is determined primarily by the rate at which the contacts are eroded by the usual arcs established therebetween. In the usual contact arrangement, the same localized areas of the contacts are exposed to the arc during each circuitinterrupting operation, and this can result in the contacts being rendered useless through excessive erosion in these localized areas while portions thereof are still relatively unimpaired.

Accordingly, an object of my invention is to provide a simple and inexpensive arrangement for distributing arcerosion over substantially the entire effective surface of a contact so as to prevent such erosion from being concentrated on only a localized portion of the contact surface.

Another object is to provide an erosion-distributing arrangement which automatically operates upon successive operations of the circuit breaker to present a different portion of the contact surface for arcing.

Another object is to provide an arrangement of this type which does not interfere with opening of the moving contact at the desired high speed and does not require critical adjustments to produce the desired distribution of arcerosion.

In carrying out my invention in one form, I provide a circuit breaker which comprises a first contact and a second contact movable along a predetermined path into and out of engagement with the first contact. Fixed to the second contact and projecting therefrom in a direction transverse to this predetermined path is rod structure that has peripherally-spaced knurls on its outer periphery. A movable actuating member is provided for transmitting opening and closing motion to the second contact, and the rod structure is rotatably mounted on this movable actuating member. The rod structure is caused to rotate on the actuating member in response to movement of the rod structure during opening motion of the second contact by means including a coiled spring having an outer peripheral portion that is engaged by said knurls during opening motion of the second contact.

For a better understanding of my invention reference may be had to the following description taken in conjunction with the accompanying drawings, wherein:

PKG. 1 is an end view of a circuit breaker embodying one form of my invention.

FIG. 2 is a sectional View taken along the line 22 of PEG. 1. The operating mechanism for the interrupter is shown in schematic form in FIG. 2.

FIGS. 3 and 4 are enlarged detailed views of certain parts of the interrupter at particular instants during opening of the interrupter.

PEG. 5 is an enlarged sectional view taken along the line 5-5 of FIG. 1.

Referring now to FIG. 1, the interrupter shown therein comprises two stationary contact assemblies disposed in laterally spaced-apart relationship. These stationary contact assemblies 10 are connected together in seriescircuit relationship by a conductive cross-bar in the form of a rod 12 of suitable conductive material carrying the movable contacts 14 of the circuit breaker at its opposite ends. Each of these movable contacts 1 comprises a sleeve of arc-resistant metal suitably bonded to a reduced diameter portion of the rod 12. Each of these movable contacts 14- is movable into and out of engagement with its mating stationary contact assembly 10 along the arcuate path 15 shown in FIG. 2. The rod 12, it will be noted projects from the movable contacts 14- transversely with respect to this arcuate path 15.

Each stationary contact assembly it? comprises a conductive stud l6 and a pair of contact fingers '18 pivotally mounted on the stud 16. The stud extends through a stationary frame of insula ing material and is fixedly mounted thereon. Preferably, this mounting comprises a nut 22 threaded onto the upper end of the stud and clamping the frame 2i) between the nut and a shoulder provided on the stud. Referring to FIG. 2, the contact fingers 13 are pivotally mounted at their upper ends on the stud l6 and are biased toward each other by suitable compression springs 24' disposed behind the fingers 18. These compression springs 24 are preferably carried by a guide pin 26 extending freely through registering openings provided in the stud do and fingers 18. Each compression spring is disposed between a stop 27 on the outer end of the pin 26 and the pivoted finger contacts 13. The lower end of each finger contact 18 is preferably provided with a facing 29 of are resistant metal which bears against the movable contact 1 during the early stages of opening movement and the final stages of closing movement of the movable contact 14.

The conductive cross-bar 12 and the movable contacts 4 at the ends of the cross-bar 12 are carried by laterallyspaced actuating arms 30 of insulating material. As shown in FIG. 2, these arms are mounted at their right hand end on stationary pivots 31 that are carried on supporting brackets 32 fixed to the bottom Wall of the stationary frame 20. The arms 38 are coupled together by a pin 36 that extends between the arms 38 and is suitably fixed to each arm to maintain a fixed lateral spacing between the arms 34 The movable contacts 14 are prevented from shifting laterally with respect to the actuating arms 30 by suitable cotter pins 37 and washers 38 disposed at the inner side of each of the actuating arms. The cross-bar is, however, freely rotatable about its axis 12a on the actuating arms 36 inasmuch as the opening in each actuating arm 34 that receives the cross-bar is considerably larger than the outer diameter of the crossbar and is capable of acting as a bearing for the cross-bar.

Since the operating mechanism of the circuit breaker constitutes no part of the present invention and can be of any suitable conventional form, it has been shown in schematic form only. This schematically-shown operating mechanism comprises a solenoid 4% having an armature 4-2 connected to the actuating arms by means of an operating rod 43 pivotally connected at its lower end to the cross-pin 36. A suitable tension spring 46 coupled to the armature biases the actuating arms 30 in a clockwise direction about their pivot 31 to normally hold the contacts 14 in their solid-line fully-closed position of FIG. 2. When the winding 47 of the solenoid is energized, as by closing a switch 48 in series therewith, it drives the armature 42 downwardly and thus pivots the actuating arms 3% in a counterclockwise opening direction about their pivots 31. Such opening action continues until the actuating arms have reached their dotted line fully-open position of FIG. 2, where they engage suitable stops 58 fixed to the bottom plate of frame 2%). Closing of the circuit breaker is effected by opening the control switch 48 to de-energize the solenoid, thus permitting the closing spring 46 to return the actuating arms 30 and the contacts 14 to their solid line closed position of FIG. 2.

When the movable contacts 14 separate from their mating stationary contacts 19 during an opening operation, an arc is established between each pair of these contacts.

This are is quickly extinguished in the oil in which the interrupter is submerged, but it usually persists for a sufiicient length of time to cause some erosion of the peripheral surface of the movable contact 14. This erosion tends to take place in the localized regions which were last in engagement when the contacts parted. If these same localized regions are eroded on each interruption, the arc-erosion that occurs with repeated operations of the interrupter can result in loss of contact pressure and cause the contact to fail while other regions of the contact are still relatively unimpaired.

In accordance with the present invention, 1 provide means for distributing the arc-erosion from repeated interrupting operations over substantially the entire effec= tive surface of each of the contacts 14. This erosiondistributing means comprises a tightly coiled metallic spring 50 shown fixed to the bottom plate of the stationary frame 24?. As will soon be explained, this spring 59 coacts with peripherally-spaced knurls 52 on the outer periphery of cross-bar 12 to elfect a partial rotation of the crossbar 12 about its longitudinal axis 12a during movement of the cross-bar through the final stages of each contact-opening operation.

The manner in which such rotation of the cross-bar vl2 is produced is illustrated in the detailed view of FIG. 3, Where the cross-bar 12 is shown at the instant it first engages the top of the coiled spring 50. This engagement is shown occurring on a knurl 52a. Once this engargement has occurred, further opening motion of the actuating arms 30 causes the central axis 12a of the crossbar 12 to continue moving downwardly, but the knurl 52a is temporarily prevented from following due to its engagement with the top of the spring 50. This relative motion between the knurl 52a and axis 12a causes the cross-bar to rotate about its axis in a counterclockwise direction, displacing the top portion of the spring slightly to the right. Eventually, as opening movement motion of the actuating arm 30 continues, the knurl 52a moves out of engagement with the top of spring 50, but ensuing opening motion causes the next knurls 52b and 520 to successively engage the periphery of the spring 50 and to produce a slight additional amount of rotary motion of the cross-bar 12 and also additional displacement of the spring 50 to the right. The fact that the top portion of the spring 50 is deflected provides a biasing force which urges the spring surface into engagement with the knurls and thus helps to produce the added rotary motion that occurs while the knurls 52b and 520 are rolling on the periphery of the spring. The fact that the spring 50 is conical or tapered and that the engaged surface of the spring therefore extends toward'the path 15 of movement for the contact 14 is an additional factor contributing to the force urging the spring 50 into engagement with the periphery of the crossbar 12. Opening motion of the cross-bar is terminated when the actuating arms 50 engage the stops 58. In a preferred embodiment of my invention, the stops 58 are so positioned that the total rotation that occurs on each opening operation is about 40 degrees.

When the actuating arm 3% is returned from its fullyopen position of FIG. 4 toward its fully closed position of FIG. 1, the knurls slide over the turns of the spring 5% without producing significant reverse rotation of the knurled cross-bar 12. The knurls are, in effect, being lifted away from the periphery of the spring and there is little tendency for the spring to produce rotation of the cross-bar under such conditions. More important, however, is that there is no reverse rotation corresponding to the relatively large amount of rotation that was produced by engagement between the initial ltnurl 52a and the top of the spring 5d during opening motion.

Thus, since the cross-bar 12 was rotated an appreciable distance but less than a full revolution during opening movement and was rotated to little or no extent during each contact i4 is presented for arcing, as compared to the" portion exposed on the immediately-precedin-g opening-op eration. This desired relationship is unchanged by any engagement of the contact 14 with fingers in, since the two fingers 18*, in engaging the contact E4, tend to produce" rotation in an opposite direction, thus cancelling any tendency of the contact 14 to rotate While in engagement Jith the fingers.

The positioning of the coil spring Etl is not highly critical since the flexibility of the spring compensates for minor variations in spring position. But it is importanil that the spring 56 be so located that the outer edge 59 or" its top turn engages the knurled periphery of crossbar 12 at a point spaced inwardly from path of ire-yernent 15 by an amount sufficient to insure that the spring 5i? will not block opening movement of the crossbar. For permitting the desired adiustment in the location of the spring 5%}, the bottom turn so of the spring, as shown in PKG. 5, is formed of a generaily U-shaped configuration providing an elongated slot 63, between the legs of the U-shaped portion for receiving the shank of a screw 62 that is threaded into the bottom plate of the frame When the screw is loose, the longitudinal axis of the spring 543 can be shifted a limited distance along tri e frame it). When the desired position of adjustment is obtained, this screw 62 is tightened and the lower end of spring 5% is thus firmly clamped in fixed position on the frame 23.

In a preferred form of my invention, the diameter 9f the wire of which the spring 5% is formed is approximately equal to or just slightly less than the distance between adjacent knurls 52. This relationship helps to assure that; the top turn of the spring Sil will fit into the space list-ween two adjacent knurls and produce a relatively large amount of rotation of the cross-bar 12 during opening motion of the cross-bar. This dimensional relationship of the spring wire and the knurls also contributes to the desired friction between the knurls and the spring that results in rolling of the cross-bar while moving downwardly while in engagement with the side or the spring.

It will be apparent from the above description that the spring So does not interfere with separation of the conacts at the desired high speed. it is only at the very end of the opening stroke, when circuit interruption would normally have been completed, that the top of the spring 56 first engages the cross-bar 12; I

While I have shown aiid described a particular t bodiment of myinvention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention in its broader aspects, and l, therefore, intend in the appended claims to cover all such changes and modifications as tall within the true spirit and scope of my invention. 7

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric circuit breaker comprising a first COIl-f tact, a second contact movable along a predetermined path into and out of engagement with said first contact, rod structure fixed to said second contact and projecting therefrom in a direction transverse to said predetermined path, a movable actuating member for transmitting opening and closing motion to said second contact, means for rotatably mounting said rod structure on said actuating member, peripherally-spaced knurls on the outer periphery of said rod structure, arc-erosion-distributing means for presenting difierent regions of said second contact for arcing on successive opening operations, said distributing. means being responsive to movement of said rod structure near the fully-open position of said second contact for causing said rod structure to rotate on said actuating member and comprising a coiled spring having an outer peripheral portion that is engaged by said knurls during movement of said second contact.

2. The circuit breaker of claim 1 in which said coiled spring first engages the knurled periphery of said rod structure during opening motion of said second contact but only after a substantial amount or" opening motion has occurred and said rod structure is entering the final stages of said opening motion.

3. The circuit breaker of claim 1 in which said coiled spring is of a generally tubular form and in which means is provided for stationarily mounting one longitudinal end of said spring with the longitudinal axis of said spring extending transverse to said rod structure, the other longitudinal end of said spring normally being free to move laterally relative to the normal position of said longitudinal axis, said free end of the spring being positioned to engage said knurls during motion of said contact near the fully-open position of said second contact.

4. The circuit breaker of claim 3 in which said free end of the spring engages said knurls during the tinal portion of a contact-opening stroke, in which said coiled spring has a conical configuration in the region in which it is engaged by said rod structure, the conical configuration being such that the engaged surface of said spring extends in convergent relationship to the path of movement of said rod structure considered in the direction of contact-opening motion.

5. The circuit breaker of claim 1 in combination with means for adjustably mounting one end of said coiled spring on a stationary frame, said adjustable mounting means comprising a terminal portion of said spring having a generally U-shaped form defining an elongated slot between the legs of the U-shaped terminal portion, screw means extending through said slot and clamping said legs to said frame in a preselected position.

6. The circuit breaker of claim 1 in which said coiled spring is formed of wire having a diameter approximating the distance between the knurls on said rod structure.

7. An electric circuit breaker comprising a first contact, a second contact movable along a predetermined path into and out of engagement with said first contact, projecting structure fixed to said second contact and projecting therefrom in a direction transverse to said predetermined path, a movable supporting member for said second contact, means for rotatably mounting said projecting structure on said supporting member for rotation about an axis extending transverse to said predetermined path, means comprising a rotation-producing part transversely displaced from said movable contact and engageable with said projecting structure to produce rotation of said projecting structure in one angular direction in response to movement of said projecting structure in one circuit-controlling direction near the fullyopen position of said second contact, said rotation-producing part being out of engagement with said projecting structure during all motion of said second contact along said predetermined path except -for motion near said fully open position, rotating means being ineffective to produce enough rotary motion of said projecting structure in a reverse angular direction to return said projecting structure to its original angular position during movement of the projecting structure in an opposite circuit-controlling direction.

8. The circuit breaker of claim 7 in which said projecting structure comprises rod structure having peripherally-spaced knurls on its outer periphery and in which said rotation-producing part is a spring having a free end positioned to engage a knurl during circuit-controlling motion of said rod structure.

9. An electric circuit breaker comprising a first contact, a second contact movable along a predetermined path into and out of engagement with said first contact, rod structure fixed to said second contact and projecting therefrom in a direction transverse to said predetermined path, a movable actuating member for transmitting opening and closing motion to said second contact, means for rotatably mounting said rod structure on said actuating member, peripherally-spaced knurls on the outer periphery of said rod structure, arc-erosion-distributing means for presenting different regions of said second contact for arcing on successive circuit breaker opening operations, said arc-erosion-distributing means comprising a spring having a portion that engages said knurls during the final portion of a contact-opening stroke and thereby causes said rod structure to rotate on said actuating member in response to movement of said rod structure through the final portion of a contactopening stroke.

References Cited in the file of this patent UNITED STATES PATENTS 2,127,957 Ives Aug. 23, 1938 2,387,961 Wihanto Oct. 30, 1945 2,485,532 Johnson Oct. 18, 1949 2,778,893 Baker Ian. 22, 1957 

7. AN ELECTRIC CIRCUIT BREAKER COMPRISING A FIRST CONTACT, A SECOND CONTACT MOVABLE ALONG A PREDETERMINED PATH INTO AND OUT OF ENGAGEMENT WITH SAID FIRST CONTACT, PROJECTING STRUCTURE FIXED TO SAID SECOND CONTACT AND PROJECTING THEREFROM IN A DIRECTION TRANSVERSE TO SAID PREDETERMINE PATH, A MOVABLE SUPPORTING MEMBER FOR SAID SECOND CONTACT, MEANS FOR ROTATABLY MOUNTING SAID PROJECTING STRUCTURE ON SAID SUPPORTING MEMBER FOR ROTATION ABOUT AN AXIS EXTENDING TRANSVERSE TO SAID PREDETERMINED PATH, MEANS COMPRISING A ROTATION-PRODUCING PART TRANSVERSELY DISPLACED FROM SAID MOVABLE CONTACT AND ENGAGEABLE WITH SAID PROJECTING STRUCTURE TO PRODUCE ROTATION OF SAID PROJECTING STRUCTURE IN ONE ANGULAR DIRECTION IN RESPONSE TO MOVEMENT OF SAID PROJECTING STRUCTURE IN ONE CIRCUIT-CONTROLLING DIRECTION NEAR THE FULLYOPEN POSITION OF SAID SECOND CONTACT, SAID ROTATION-PRODUCING PART BEING OUT OF ENGAGEMENT WITH SAID PROJECTING STRUCTURE DURING ALL MOTION OF SAID SECOND CONTACT 